KR20000011230A - Multi-domain liquid crystal display device - Google Patents

Abstract

PURPOSE: A multi domain LCD(liquid crystal display) is provided to improve an aperture rate and a viewing angle by forming an auxiliary electrode used as distortion of electric field and light shading on an upper plate. CONSTITUTION: The LCD comprises a first substrate and a second substrate(31, 33); a liquid crystal layer formed between the first and second substrates(31, 33); a plurality of gate and data wires(1, 3) defining a pixel region and formed on the first substrate; a TFT(thin film transistor) having a gate electrode(11), a semiconductor layer(5) and source/drain electrodes(7, 9) and formed at crossing part of the gate and the data wires; a pixel electrode(13) formed in the pixel region; an auxiliary electrode(27) formed on the second substrate(33); a color filter layer(23) formed on the auxiliary electrode(27); and a common electrode(17) formed on the color filter layer.

Description

Multi-domain liquid crystal display device {MULTI-DOMAIN LIQUID CRYSTAL DISPLAY DEVICE}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a multi-domain liquid crystal display device in which an auxiliary electrode is formed on a top plate to distort an electric field and serve as light blocking.

Recently, a liquid crystal display device for driving a liquid crystal by side electrodes electrically insulated from the pixel electrode without aligning the liquid crystal has been proposed. 1 is a cross-sectional view of a unit pixel of the above-described conventional liquid crystal display device.

In a conventional liquid crystal display device, a plurality of data wirings and gate wirings are vertically and horizontally formed on a first substrate to divide the first substrate into a plurality of pixel regions, and are formed in each of the pixel regions and include a gate electrode, a gate insulating film, and a semiconductor A thin film transistor (TFT) composed of a layer, a source electrode, a drain electrode, and the like applies an image signal transmitted from the data wiring to the pixel electrode 13 formed on the insulating layer 4. The side electrode 15 is formed on the gate insulating film so as to surround the pixel electrode 13, the insulating layer 4 is formed over the entire substrate, and a part of the pixel electrode 13 is described as the side electrode. It forms so that it may overlap with (15) (FIG. 1).

Alternatively, as another modification, a pixel electrode is formed on the gate insulating film described above, an insulating layer is formed over the entire substrate, and then side electrodes are formed to overlap with a part of the pixel electrode. There is also proposed a structure for dividing the pixel region by etching the electrode into a specific shape.

The common electrode 17 is formed on the second substrate to apply an electric field to the liquid crystal layer made of liquid crystal molecules together with the pixel electrode 13. The side electrode 15 formed around the pixel electrode 13 and the slit region 19 of the second substrate distort the electric field applied to the liquid crystal layer to variously drive the liquid crystal molecules in the unit pixel. This means that when a voltage is applied to the liquid crystal display, the dielectric energy due to the distorted electric field places the liquid crystal director in a desired direction.

However, the above-described liquid crystal display device requires a slit 19 on the pixel electrode 13 or the common electrode 17 for uniform driving of liquid crystal molecules, and drives the liquid crystal molecules more stably by increasing the area of the slit. You can. On the other hand, if there is no slit or the width of the slit is small, the electric field distortion necessary for domain division is weak. Therefore, the time required for the director of the liquid crystal to reach a stable state when a voltage higher than the threshold voltage (V _th ) is applied is determined. Relatively long. In particular, the response time may take about 100 msec or more. At this time, since a range of the liquid crystal director parallel to the transmission axis of the polarizer exists and a foreground occurs, a decrease in luminance due to this is also pointed out as a problem. The liquid crystal texture may have an irregular shape according to the surface state of the liquid crystal display device.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems of the prior art, and an object thereof is to provide a multi-domain liquid crystal display device having a wide viewing angle characteristic due to a multi-domain effect and a high luminance characteristic due to stable movement of liquid crystal molecules when voltage is applied. do.

In order to achieve the above object, the multi-domain liquid crystal display device according to the present invention, the opposing first substrate and second substrate, the liquid crystal layer formed between the first substrate and the second substrate, and the first A thin film transistor comprising a plurality of gate wirings and data wirings formed vertically and horizontally on a substrate to define pixel regions, and formed at intersections of the gate wirings and data wirings, the thin film transistors comprising a gate electrode, a semiconductor layer, and a source / drain electrode; A pixel electrode formed in the pixel region, an auxiliary electrode formed on the second substrate, a color filter layer formed on the auxiliary electrode, a common electrode formed on the color filter layer, and the first substrate And an alignment film formed on at least one of the second substrates.

The multi-domain liquid crystal display device of the present invention further includes an overcoat layer and a protective film under the pixel electrode on the color filter layer, wherein the slit region or hole is formed in the pixel electrode.

In addition, since the pixel region and the alignment layer are divided into at least two regions, the liquid crystal molecules of the liquid crystal layer exhibit different driving and alignment characteristics on each region, and the alignment layer is non-rubbing or rubbing. Or photoalignment treatment.

1 is a cross-sectional view of a conventional liquid crystal display device.

2A, 2B, 2C, 2D, and 2E are plan views showing modifications according to one embodiment of the present invention.

3A, 3B, 3C, 3D, 3E, 3F, 3G, and 3H are plan views showing modifications according to other embodiments of the present invention.

4A, 4B, 4C, and 4D are cross-sectional views of multi-domain liquid crystal display devices according to the first, second, third, and fourth embodiments of the present invention.

5 is a plan view of a multi-domain liquid crystal display device according to another embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

1: gate wiring 3: data wiring

4: insulating layer 5: semiconductor layer

7 source electrode 9 drain electrode

11 gate electrode 13 pixel electrode

15: side electrode 17: common electrode

19: open area 23: color filter layer

25 shading layer 27 auxiliary electrode

29: retardation film 31: the first substrate

33: second substrate 35: gate insulating film

37: shield 39: contact hole

43: storage electrode 45: overcoat layer

51: electric field induction window (hole or slit)

Hereinafter, a multi-domain liquid crystal display device according to the present invention will be described in detail with reference to the drawings.

2A, 2B, 2C, 2D, 2E, and 3A, 3B, 3C, 3D, 3E, 3F, 3G, and 3H are plan views illustrating modified examples of the multi-domain liquid crystal display device according to an exemplary embodiment of the present invention. 4A, 4B, 4C, and 4D are cross-sectional views of one embodiment taken along the line II ′ of FIG. 3A.

As shown in the above drawings, the multi-domain liquid crystal display device of the present invention is formed vertically and horizontally on the first substrate 31 and the second substrate 33 and the first substrate 31 to form a plurality of first substrates. A plurality of data wirings 3 and gate wirings 1 divided into pixel regions, and pixel regions on the first substrate 31, respectively, and formed with a gate electrode 11, a gate insulating film 35, a semiconductor layer 5, A thin film transistor including an ohmic contact layer and source / drain electrodes 7 and 9, a passivation layer 37 formed over the entire first substrate 31, and a drain electrode 9 on the passivation layer. And a pixel electrode 13 formed to overlap the thin film transistor and / or the data wiring 3 and the gate wiring 1.

And, the auxiliary electrode 27 for distorting the electric field and acts as a light shielding to block the light leakage from the gate wiring 1, the data wiring 3, and the thin film transistor on the second substrate 33, The color filter layer 23 formed on the auxiliary electrode 27, the common electrode 17 formed on the color filter layer 23, and the first substrate 31 and the second substrate 33 are formed between the color filter layer 23. It consists of a liquid crystal layer.

In the above-described multi-domain liquid crystal display device, a protective film may be formed to prevent short of the auxiliary electrode 27 and the common electrode 17 and to reduce reliability due to the reaction of the color filter layer 23 and the liquid crystal layer. In this case, the overcoat layer is formed on the color filter layer 23 and the common electrode 17 is formed thereon.

The auxiliary electrode 27 is formed of Cr having good conductivity, and an element OP Amp for providing an amplified signal is provided to apply a voltage. For example, in the case of 5 Volt driving, when the voltage of | 0 to 5 | Volt is applied to the pixel electrode 13 and the voltage V _com of the common electrode 17 is 0 Volt, the auxiliary electrode 27 ) Is applied a voltage of | V _com -α |. α has a value of 0 <α <V _op (operating voltage), and preferably has a value of 0 <α <V _th (threshold voltage). Therefore, when the value of α has a large value within the above range, the potential difference between the common electrode 17 and the auxiliary electrode 27 is increased, so that the distortion effect of the electric field formed in the multi-domain liquid crystal display element is increased.

In order to manufacture a multi-domain liquid crystal display device having the above structure, first, a gate electrode 11, a gate insulating film 35, a semiconductor layer 5, an ohmic contact layer and a source are respectively formed in each pixel region of the first substrate 31. A thin film transistor consisting of the drain electrodes 7 and 9 is formed. At this time, a plurality of gate wirings 1 and data wirings 3 which divide the first substrate 31 into a plurality of pixel regions are formed.

The gate electrode 11 and the gate wiring 1 are formed by stacking and patterning a metal such as Al, Mo, Cr, Ta, or Al alloy by a sputtering method, and forming a gate insulating film thereon. 35) is formed by laminating SiN _X or SiO _X by PECVD and patterning.

Subsequently, the semiconductor layer 5 and the ohmic contact layer are formed by laminating a-Si and n ⁺ a-Si, respectively, by PECVD (Plasma Enhancement Chemical Vapor Deposition). In addition, the gate insulating film 35 and a-Si and n ⁺ a-Si can be continuously deposited by PECVD and patterned. Then, metals such as Al, Mo, Cr, Ta, or Al alloys are stacked and patterned by sputtering to form data wirings 3 and source / drain electrodes 7 and 9.

Subsequently, the protective film 37 is formed of a material such as BCB (BenzoCycloButene), an acrylic resin, a polyimide compound, SiN _X or SiO _X and the like, and the ITO (indium) is formed over the first substrate 31. Tin oxide) is stacked by the sputtering method and then patterned to form the pixel electrode 13. The pixel electrode 13 is electrically connected to the source / drain electrodes 7 and 9 of the thin film transistor through the contact hole 39.

At this time, the pixel electrode 13 or the passivation layer 37 is patterned to form an electric field induction window 51 such as a slit or a hole, thereby producing an electric field distortion effect. 4A and 4B) Also, as shown in FIGS. 4C and 4D, the gate insulating film 35 may be partially or completely patterned to form the field induction window 51.

Metals are deposited on the second substrate 33 by a sputtering method, etched to form an auxiliary electrode 27, and the color filter layer 23 is formed such that R, G, and B (red, green, blue) elements are repeated for each pixel. Form. The auxiliary electrode 27 may be a metal having high conductivity, and Cr is most preferable. In the case of forming the overcoat layer on the color filter layer 23, the resin is formed over the entire second substrate, and the common electrode 17 is formed of a transparent electrode such as ITO, like the pixel electrode 13. The liquid crystal is injected between the first substrate 31 and the second substrate 33 to complete the multi-domain liquid crystal display device.

The liquid crystal described above may use a liquid crystal having negative or positive dielectric anisotropy, and may add a chiral dopant.

The pixel electrode 13 described above has various forms as shown in FIGS. 2B, 2C, 2D, 2E, and 3A, 3B, 3C, 3D, 3E, 3F, 3G, and 3H in addition to the through electrode shown in FIG. 2A. The electric field induction window 51 is formed to implement a multi-domain effect. That is, the pattern is divided into 2 domains by patterning the pattern horizontally, vertically, and diagonally, or simultaneously patterning the x-shape, the + -shape, the double-wire (Fig. 3g) shape, the o-shape, and the x- and + -shape simultaneously. By implementing the effect divided into 4 domains and multi-domain, it is also possible to apply independently or mixed on both substrates. Although not shown in the drawings, the above-described field induction window may also be formed on the common electrode 17 of the second substrate.

The voltage V _com is applied to the auxiliary electrode 27 by forming Ag-Dotting portions at each corner of the driving region of the liquid crystal display element on the first substrate 31. An electric field is applied to drive the liquid crystal by the vertical potential difference. The voltage V _com is applied by connecting the Ag-Dotting portion and the auxiliary electrode 27 at each corner.

In addition, the retardation film 29 is formed by stretching the polymer on at least one of the first and second substrates 31 and 33.

The retardation film 29 is a negative uniaxial film, and is formed of a uniaxial material having one optical axis, and serves to compensate for a user's feeling in a direction perpendicular to the substrate and a change in viewing angle. Accordingly, the viewing angle in the left and right directions can be more effectively compensated by widening the region without gray inversion, increasing the contrast ratio in the oblique direction, and forming one pixel in a multi-domain.

In the multi-domain liquid crystal display device of the present invention, in addition to the negative uniaxial film described above, a negative biaxial film may be formed as a retardation film, and a negative biaxial film composed of a biaxial material having two optical axes. Compared to the uniaxial film described above, a wide viewing angle characteristic can be obtained.

After attaching the retardation film, a polarizer (not shown) is attached to both substrates, and the polarizer may be formed integrally with the retardation film.

5 is a plan view of a multi-domain liquid crystal display device according to another exemplary embodiment of the present invention.

As shown in the drawings, the multi-domain liquid crystal display device according to the present invention has a high-aperture-rate thin film transistor (L-lined Thin Film Transistor) structure, and forms a storage electrode 43 so as to overlap with the gate wiring 1, thereby storing By forming the capacitor and forming the TFT in the L-shape on the gate wiring 1, the aperture ratio is improved compared with the conventional thin film transistor, and between the gate wiring 1 and the drain electrode 9 The parasitic capacitors generated can be reduced.

In addition, the multi-domain liquid crystal display device of the present invention forms an alignment film (not shown) over the entirety of the first substrate and / or the second substrate. In this case, a material such as polyamide or polyimide compound, PVA (polyvinylalcohol), polyamic acid or SiO ₂ may be used as the alignment material constituting the alignment layer. In the case of determining the orientation direction by use, any material suitable for other rubbing treatments can be applied.

In addition, the alignment layer may be formed of a photoreactive material, that is, a material such as PVCN (polyvinylcinnamate), PSCN (polysiloxanecinnamate), or CelCN (cellulosecinnamate) -based compound to form a photoalignment film, and other optical alignment treatment Any material suitable for is applicable. The optical alignment film is irradiated with light at least once to determine the alignment direction or pretilt angle direction and pretilt angle formed by the director of the liquid crystal molecules at the same time. It ensures the orientation stability of the liquid crystal. As for the light used for the optical alignment, light in the ultraviolet region is suitable, and any light among non-polarized light, linearly polarized light, and partially polarized light may be used.

The rubbing method or the photo-alignment method may be applied to only one of the first substrates or the second substrates, or may be treated on both substrates, or may be subjected to different alignment treatments on both substrates, or only an alignment film is formed and the alignment treatment is performed. It is also possible not to.

In addition, by performing the above-described alignment process, a multi-domain liquid crystal display device divided into at least two regions may be formed so that the liquid crystal molecules of the liquid crystal layer may be differently aligned on each region. That is, the multi-domain effect is realized by dividing each pixel into four regions, such as + or × characters, or by dividing them into horizontal, vertical, or diagonal lines, and by forming different alignment processes or orientation directions in each region and each substrate. do. At least one of the divided regions may be a non-oriented region, and the entire region may be a non-oriented region.

In the multi-domain liquid crystal display device of the present invention, the long axis of the liquid crystal molecules constituting the liquid crystal layer is horizontally aligned (homogeneous alignment) in which the first and second substrates are oriented in parallel with each other. Vertically oriented homeotropic alignment is possible, and the tilted alignment or twisted alignment is oriented at a specific angle with respect to the substrate surface of the first substrate or the second substrate. alignment, any type of orientation and mode, such as hybrid alignment oriented horizontally with respect to the substrate surface of either the first substrate or the second substrate and perpendicular to the substrate surface of the other substrate. This has the advantage of being possible.

The multi-domain liquid crystal display device of the present invention can simplify the electrode pattern process and secure the aperture ratio by forming an auxiliary electrode on the top plate which distorts an electric field and also serves as a light shielding function, and adjusts the voltage of the auxiliary electrode. By increasing the distortion effect there is an effect to implement a wide viewing angle.

In addition, when the alignment process is performed, a fast response time and a stable liquid crystal structure can be obtained by the pretilt and anchoring energy formed. As a result, the foreground is removed, thereby obtaining an effect of increasing luminance.

Claims (36)

Opposing first and second substrates, A liquid crystal layer formed between the first substrate and the second substrate; A plurality of gate wirings and data wirings formed vertically and horizontally on the first substrate to define pixel regions; A thin film transistor formed at an intersection point of the gate line and the data line and formed of a gate electrode, a semiconductor layer, and a source / drain electrode; A pixel electrode formed in the pixel region, An auxiliary electrode formed on the second substrate; A color filter layer formed on the auxiliary electrode; A common electrode formed on the color filter layer; A multi-domain liquid crystal display device comprising an alignment film formed on at least one of the first substrate and the second substrate. The multi-domain liquid crystal display of claim 1, further comprising a passivation layer under the pixel electrode. The multi-domain liquid crystal display device according to claim 2, wherein a hole is formed in said protective film. The multi-domain liquid crystal display device according to claim 1, further comprising an overcoat layer on the color filter layer. The multi-domain liquid crystal display device according to claim 1, wherein the material constituting the pixel electrode is indium tin oxide (ITO). The multi-domain liquid crystal display device according to claim 1, wherein the auxiliary electrode is made of metal. 7. The multi-domain liquid crystal display device according to claim 6, wherein the metal is Cr. The multi-domain liquid crystal display of claim 1, wherein the material constituting the common electrode is made of indium tin oxide (ITO). The multi-domain liquid crystal display of claim 1, wherein a slit region is formed in the pixel electrode. The multi-domain liquid crystal display device of claim 1, wherein the pixel electrode is patterned. The multi-domain liquid crystal display device according to claim 1, wherein the pixel region is divided into at least two regions so that the liquid crystal molecules of the liquid crystal layer exhibit different driving characteristics on each region. The multi-domain liquid crystal display device according to claim 1, wherein the alignment film is divided into at least two regions so that the liquid crystal molecules of the liquid crystal layer exhibit different alignment characteristics on each region. 13. The multi-domain liquid crystal display device according to claim 12, wherein at least one of the regions of the alignment film is aligned. 13. The multi-domain liquid crystal display device according to claim 12, wherein all of the regions of the alignment film are not aligned. The multi-domain liquid crystal display device according to claim 12, wherein at least one of the regions of the alignment layer is rubbed in alignment. The method of claim 15, wherein the material constituting the alignment layer is selected from the group consisting of polyimide and polyamide-based compounds, polyvinylalcohol (PVA), polyamic acid, and SiO ₂ . A multi-domain liquid crystal display device. 13. The multi-domain liquid crystal display device according to claim 12, wherein at least one of the regions of the alignment layer is optically aligned. The multi-domain liquid crystal display device according to claim 17, wherein the material constituting the alignment layer is selected from the group consisting of polyvinylcinnamate (PVCN), polysiloxanecinnamate (PSCN), and cellulosecinnamate (CelCN) -based compounds. 18. The multi-domain liquid crystal display device according to claim 17, wherein the optical alignment uses light in an ultraviolet region. 18. The multi-domain liquid crystal display device according to claim 17, wherein the optical alignment irradiates light at least once. The multi-domain liquid crystal display device according to claim 1, wherein the liquid crystal constituting the liquid crystal layer is a liquid crystal having positive dielectric anisotropy. The multi-domain liquid crystal display device according to claim 1, wherein the liquid crystal constituting the liquid crystal layer is a liquid crystal having negative dielectric anisotropy. The multi-domain liquid crystal display device according to claim 1, wherein the liquid crystal constituting the liquid crystal layer is horizontally aligned with respect to the substrate surface of the first substrate or the second substrate. The multi-domain liquid crystal display device according to claim 1, wherein the liquid crystal constituting the liquid crystal layer is vertically aligned with respect to the substrate surface of the first substrate or the second substrate. The multi-domain liquid crystal display device according to claim 1, wherein the liquid crystal constituting the liquid crystal layer is inclined with respect to the substrate surface of the first substrate or the second substrate. The multi-domain liquid crystal display device according to claim 1, wherein the liquid crystal constituting the liquid crystal layer is twist-oriented with respect to the substrate surface of the first substrate or the second substrate. The liquid crystal constituting the liquid crystal layer according to claim 1, wherein the liquid crystal constituting the liquid crystal layer is horizontally oriented with respect to the substrate surface of any one of the first or second substrates described above, and is perpendicular to the substrate surface of the other substrate. A multi-domain liquid crystal display device. The multi-domain liquid crystal display device of claim 1, further comprising: forming a negative uniaxial film on at least one of the first and second substrates. The multi-domain liquid crystal display device of claim 1, further comprising: forming a negative biaxial film on at least one of the first and second substrates. The multi-domain liquid crystal display device according to claim 1, wherein the liquid crystal layer comprises a chiral dopant. A first substrate and a second substrate facing each other, a data wiring supplied with a data signal on the first substrate, a pixel electrode for driving a liquid crystal, and a gate formed to intersect the data wiring to define a pixel region. A multi-domain liquid crystal display device comprising wiring and a light shielding auxiliary electrode formed on the second substrate. 32. The multi-domain liquid crystal display device of claim 31, further comprising an L-lined thin film transistor formed at an intersection point of the gate line and the data line. 32. The multi-domain liquid crystal display device of claim 31, further comprising forming a gate insulating film and a protective film on the first substrate. 32. The multi-domain liquid crystal display device according to claim 31, wherein the pixel electrode has an electric field induction window therein. The multi-domain liquid crystal display device according to claim 33, wherein the protective film has an electric field induction window therein. 34. The multi-domain liquid crystal display device according to claim 33, wherein the gate insulating film has an electric field induction window therein.